Polymers acting as both an electrolyte and a separator are of tremendous interest because of their many virtues, such as no leakage, flexible geometry, excellent safe performance, and good compatibility with electrodes, compared with their liquid counterparts. | Physical-chemical and electrochemical properties of sodium ion conducting polymer electrolyte using copolymer poly(vinylidene fluoride- hexafluoropropylene) (PVDF-HFP)/ polyethylene oxide (PEO)